Prior to the present invention, resilient boot seals molded from rubber and plastic materials for enclosing and protecting mechanisms such as constant velocity universal joints have been designed with various specialized constructions to control and improve the action of the boot seal during the various geometric motions of the universal joint. The universal joint boot seal disclosed in U.S. Pat. No. 4,456,269 issued to Werner Krude et al June 26, 1984, for example, is provided with external ribs extending as webs connecting an attachment end portion and an adjacent convolution to reinforce and strengthen areas of the seal. Further, this boot seal has radial inner projections which act as stop means when the joint is articulated toward particular limits. In U.S. Pat. No. 4,702,483 issued to Milio Ukai, et al Oct. 27, 1987, a circumferential convex strip is provided on an inner surface of at least one of the convolutions of a boot seal for a universal joint to control the manner in which the boot collapses under bending operations to prevent the entrapment of certain convolutions between a first convolution and a drive shaft. U.S. Pat. No. 4,573,693 issued to Rikizo Nakata et al Mar. 4, 1986, discloses a boot seal having a special wear resistant coating on the exterior surface thereof to enhance the durability of the seal.
The present invention is of the general category of U.S. Pat. No. 4,456,269 (Krude et al), U.S. Pat. No. 4,702,483 (Ukai et al) and U.S. Pat. No. 4,573,693 (Nakata et al) cited above, but provides new and improved seal construction for reducing seal abrasion and wear to enhance boot seal durability and service life. More particularly, the preferred embodiment of this invention comprises a boot seal which may be molded from a rubber or plastic material into a bellows-like unit having a series of convolutions and which decreases in diameter between spaced attachment end portions. Each convolution is formed with inclined side walls which extend radially inward and connect at roots that provide live hinges which bend during operation of the universal joint or other protected mechanism. With the present invention, a circular arrangement of axially extending and resilient ribs are molded on at least one side face of one of the convolutions that extend to terminal contact faces normally spaced near the adjacent side face of the neighboring convolution. During large bend angles of a universal joint protected by this seal, the contact faces of some of the rib faces physically engage the adjacent face of the ribs and bend as relative turning movement occurs between the convolutions. Frictional wear thus primarily occurs in the contact ribs which are sacrificial instead of at the side faces of the convolution. This reduces abrasion and wear of the boot seal to lengthen seal service life.
It is a feature, object and advantage of the present invention to provide a new and improved multi-convoluted boot seal of resilient material which has axially extending flexible contact ribs arranged in a pattern on at least one of the side walls of a convolution that terminate in contact faces normally adjacent to a facing side wall of a neighboring convolution which bend on contact therewith during relative movement including relative turning of these convolutions.
It is another feature and object of this invention to provide a multi-convoluted boot seal of resilient material with flexible contact ribs to flex and bend during operation of a device enclosed by the boot seal to reduce frictional abrasion between adjacent side walls to enhance boot seal service life.